1. Field of the Invention
The present invention relates generally to the art of winding equipment. More specifically, it relates to equipment for winding strips of elongate, pliable material, such as paper or plastic, into coreless rolls. Still more specifically, the preferred embodiment of the present invention relates to equipment for winding a strip of plastic bags into coreless rolls.
2. Description of the Prior Art
Equipment for winding material into core-containing and coreless rolls is well known in the art. For purposes of illustrating such prior art, one particular type of coreless plastic bag winder will be described, i.e., a winder for plastic garbage or trash bags, kitchen wastebasket liners, food storage bags, etc.
In such prior art winder, a continuous strip of bags is fed to the winder, and the winder prepares coreless rolls therefrom. The bags themselves are produced in upstream bag making equipment which will be only briefly described because the method of making the bags is not critical to the present invention.
In most conventional bag making equipment a tube of plastic film is extruded through an extruding die, and the tube is then flattened before it enters the bag machine. In the bag machine the film is sealed across its width to form the bottom of the finished product. The open top of the bag can be formed in two different types of bag machines. The first is to simply cut the bag. In this type of bag machine, individual bags are formed which are typically folded and placed into suitable packaging for the individual or institutional consumer. In the other type of bag machine, the top is formed by perforating the bag across its width. The bag is then folded longitudinally, either before or after the perforation step, to provide a continuous strip of connected and folded bags. Such bags are then wound into a core-containing or a coreless roll. It is the latter type of bag machine with which the winder of the present invention is particularly useful.
The winder which is most similar to the winder of the present invention is the winder which has been sold by Custom Machinery Design, Inc. of Little Chute, Wisconsin for the past few years. That winder will be described in some detail here. Such winder includes a dancer mechanism to sense the tension of the strip of bags being fed to the winder, the dancer mechanism including a connection to the winder drive motor, whereby the speed of the winder can be "slaved" to the output speed of the upstream bag making equipment.
The prior art winder also includes haul-off nip rollers, to feed the strip into the winder, and an interrupt section to periodically break the perforations between certain bags in the strip. The frequency of the interruption is determined by the number of bags to be included in each roll. For example, if the roll is to contain twenty bags, the interrupt section will break every twentieth perforation.
Downstream of these sections, the prior art winder includes a three-spindle turret assembly. The winder is designed so that the leading end of one strip of bags is attached to a first spindle when the turret is in a first position. The turret then rotates 120.degree. so that the first spindle is in a second position where the strip is wound into a coreless roll. Following completion of the roll winding, the turret rotates again to a removal station where the roll is pushed off the first spindle by a push-off palm for subsequent packaging. While one roll is being started, a second roll is being wound and a third roll is being removed, etc.
Several other features of the prior art winder should be mentioned here. First, the spindles of the machine are tapered and include a plurality of air holes through which air can be selectively injected. The taper and air injection assist in the removal of the coreless roll. Second, a belt is provided below the turret which includes a movable nose roll. The roll being wound on the spindle stays in contact with the belt to improve the quality of the rolled product, and as the diameter of the roll increases during winding, the belt moves to accommodate roll expansion. This bottom belt is just one of a series of bottom belts used in the prior art machine from the inlet to the outlet of the winder.
While the above-mentioned prior art winder represents a significant improvement over earlier winders for plastic bags, several drawbacks exist. One drawback is the method by which the leading end of a strip of bags is attached to a spindle. This has been accomplished by employing an air horn, kick-roll mechanism. The kick-roll is a pneumatic activated roller located beneath a traveling belt at the area near the transfer location. At the time of transfer, the roller would be extended by a piston rod to quickly push against the belt to "flip" the leading edge of the strip of bags up into the air above the lower belt. At the same time, an air horn would descend around the spindle, the air horn being a half-cylinder containing air ports on one edge. The combination would direct the leading edge of the bag strip around the spindle and tuck it into its own nip to create the attachment. This system, while being better than earlier systems, suffers from drawbacks including complicated hardware (i.e., the kick-roll mechanism and air horn). Moreover, because of the high speeds utilized in my prior art machines, if the air horn, kick-roll system failed to properly attach the moving plastic web to the spindle, a great deal of waste would occur before the next strip would arrive at the transfer position.
Another drawback of the prior machine relates to the spindles themselves and the need to have a complex air supply system for each. Moreover, because the spindle is critical to the integrity of the roll, any tendency of the roll to stick on the spindle or any failure of the air supply system would also lead to waste, or finished products of undesirable quality.
Finally, the prior art machine is fairly large, primarily because of the traveling belt systems and the mechanism required for the air horn, kick-roll combination.
A winder which overcomes the aforementioned disadvantages of the prior art winder would represent a significant advance in the art.